1. Field of the Invention
The present invention relates to a device including two parts, one of which is a cantilever, connected to each other and movable relative to each other. More particularly, the present invention relates to a scanning system including such a device.
2. Description of Related Art
Probe-based scanning systems, also referred to as scanning probe microscopes (SPM), are used for surface analysis of samples with high resolution. SPM systems are particularly used in nanotechnology-related applications including bio-sensors, data storage, metrology, lithography and nano-fabrication. The measurement principle of these systems is based on monitoring the interaction between a cantilever and a sample. The cantilever may be provided with or without a probe tip, wherein the latter is used, for example, in bio-sensing applications. The cantilever is scanned over the surface to be analyzed, and the displacement or motion of the cantilever is detected in order to provide an image of the surface. Depending on the type of SPM system, a surface analysis may be carried out in different modes, including static and dynamic modes. In a dynamic mode, the cantilever is actuated to vibrate or oscillate, e.g. at or near the resonant frequency of the cantilever.
In many applications including data storage, metrology, lithography and nano-fabrication, high-throughput systems are essential for commercial success. In order to meet this demand, systems incorporating parallelism are provided which employ a large number of micro cantilevers being arranged in an array. In these systems, actuating and sensing capabilities need to be integrated with respect to individual cantilevers for selectivity.
Typically, optical detection systems are used for sensing the deflection of micro cantilevers, because of their high resolution, bandwidth and independence from an actuation mechanism. However, such setups are expensive and bulky, and therefore may be not suitable for selectively detecting the deflection of cantilevers of a large cantilever array. Other sensing concepts which are based on e.g. thermoelectric, piezoresistive, piezoelectric, capacitive and optical waveguide based techniques may provide other solutions, as they may be fabricated in integrated form. Capacitive sensing may require large comb structures and highly sensitive electronics, and may be affected by a high leakage current. Cantilevers using optical waveguides may not be densely fabricated in two-dimensional arrays, and may furthermore be difficult to be integrated with respect to an actuation system at the cantilever level.
Concerning the individual actuation of micro cantilevers being arranged in an array, it is known to apply electrostatic techniques. However, these techniques are constrained to having a conductive substrate below the sample with the sample being very thin. Alternatively, cantilevers may be actuated by means of piezo elements being fabricated on each of them. Moreover, the application of piezo materials may not be suitable for integration on micro cantilevers which are (additionally) configured for a special-purpose characterization (e.g. electrical, magnetic, thermal etc. characterization). Furthermore, cantilevers having a piezoelectric coating for actuation (which may come along with a strain based sensor) have a high stiffness, and may therefore not be suitable for scanning soft samples.
Apart from the above-described deflection sensing and actuation mechanisms, other concepts which make use of magnetism are applied. As an example, U.S. Pat. No. 6,611,140 B1 discloses a scanning probe microscope including a magnetic element and a magnetic sensor in order to sense the displacement of a cantilever. With respect to actuation, WO 96/28706 A1 describes a scanning probe microscope including a cantilever having a magnetic material applied to the same. The microscope furthermore includes a separate solenoid which is used to generate a magnetic field, thereby causing a deflection of the cantilever. A converse actuation concept is described in WO 01/73791 A1. Here, the scanning probe microscope includes a cantilever having two legs, and a separate magnet. By passing an electric current through the legs of the cantilever, a magnetic field is generated which causes a movement of the cantilever.
The application of separate (external) solenoids or magnets may involve the generation of magnetic fields having an influence in a wide area or space, respectively. The known concepts may not be suitable for the integration of a large number of cantilevers. The influence of a wide-area magnetic field may also be present in the area of a sample and of a probe tip, which may restrict the mode of operation to a topographic characterization only. Also, a wide-area magnetic field when used on probes in an array having magneto-resistive elements for self sensing may lead to a reduced and non-uniform sensitivity among the probes.